Eocene belemnites

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Mar 7, 2009
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So, is it a belemnite? Naef thought so and placed this form in "Familie: Belemnitidae BlaINV."

Donovan says "There is disagreement on what is the last belemnoid. There are genera which are intermediate between belemnoids and sepiids. I have placed Bayanoteuthis (Eocene), which probably had a rostrum of calcite, in the Belemnoidea. But Styracoteuthis (Eocene) whose rostrum has lost all the details of its internal structure through recrystallisation, was probably of aragonite .."

As can be seen above these specimens have not lost the details of the internal structure, though there is some recrystallisation. I've started to do a proper job of polishing the sections and will post some better images a bit later.
 
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Some new photos of the very fine concentric growth rings in longitudinal and transverse sections.
 

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Architeuthoceras

Architeuthis
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Good find Hajar. They certainly have the structure of Belemnite guards. Now you have to find out why the Belemnites went extinct in the Eocene. :sly:
 
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I'm told I should look for an example showing the protoconch. "A perforated first septum with a caecum entering the protoconch would implicate spirulid or sepiid affiliations, a closed first septum would prove that it is a belemnite."
Temperatures are down, so I'll go looking!
 
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I never thought I would find myself doing microsurgery on an ancient squid, but challenged to look closely at the protoconchs of these Styracoteuthis fossils I've taken a scalpel to the attached juvenile (35 mm long as preserved). The phragmacone is recrystallized, but traces of septa can be seen. The exposed protoconch seems simple and cup-shaped.

This paper shows protoconchs in belemnites from the Late Cretaceous: http://app.pan.pl/archive/published/app53/APP53-669.pdf
 

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I've put a (sadly nondescript) Styracoteuthis in this imagined Paleogene Muscat area marine scene.
 

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I have just found this site. These fossils are very exciting and may give us an understanding of this strange group of belemnite-like coleoids. I would love to see them.
 

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